1. Field of the Invention
In its general aspect, the present invention relates to the fabrication of semiconductor devices.
In particular, the present invention relates to a process for removing residues or polymers formed on structures of semiconductor devices after etching.
2. Description of the Related Art
Conventional fabrication of electronic devices typically involves placing numerous device structures on a single monolithic substrate. The device structures are then electrically interconnected by means of conductive structures formed in layers on the monolithic substrate. The conductive structures can be for instance horizontal metal lines and vertical conductive structures called vias between layers, with dielectric material disposed between the conductive structures so as to implement desired circuit function.
During the fabrication of semiconductor devices, it is typical to realize conductive structures, such as metal lines and vias, by etching processes, such as plasma etching.
During the etching process of semiconductor structures having a silicon oxide as dielectric layer, one or more metal layers and a photo-resist, after exposure and development of the photo-resist, residues are sometimes deposited on sidewalls of the formed conductive structures. These residues, also known as polymers, include both organic and inorganic components and need to be removed since, it is well known in the art that the presence of such residues and polymers can affect the reliability of the semiconductor devices.
However, the removal of the above polymer materials is a difficult problem in the semiconductor industry. In current fabrication processes, these polymers are later removed by cleaning processes which involve treating the semiconductor device with high cost and toxic solvents. The process flow is normally burdened with particular and complicated rinsing methodologies without which there is a very high risk of corrosion of the metal layers, resulting in large problems of defects, and from the interruption of the continuity of the metal lines.
Furthermore, the solvents used in the above mentioned cleaning processes themselves leave residues that are then difficult to remove.
It would, therefore, be desirable to provide a new process for the selective removal of residues left on a semiconductor structure after an etching process, in particular a plasma etching, which leaves the surface as clean as possible, reduces the environmental impact, and simplifies the work of choosing the machines for the production of semiconductor devices.
The present invention relates to a novel process for removing post-etch residues or polymers from the surface of semiconductor devices which comprises treating the semiconductor device with an aqueous ammonia or ammonium hydroxide solution, optionally containing ozone for a time sufficient to effectively remove said post-etch residues or polymers from the surface of the semiconductor device and rinsing the semiconductor device with ozonized water, i.e. water enriched with ozone, in which water is preferably deionized (ozone-DIW).
According to an embodiment of the present invention, the new process comprises the steps of:
treating the semiconductor device with an aqueous ammonia or ammonium hydroxide solution for a time sufficient to effectively remove said post-etch residues or polymers from the surface thereof, and then
rinsing the semiconductor device with ozonized water.
According to another embodiment of the present invention, the new process comprises the steps of:
treating the semiconductor device with ozonized water and then with an aqueous ammonia or ammonium hydroxide solution for a time sufficient to effectively remove said post-etch residues or polymers from the surface thereof, and then
rinsing the semiconductor device with ozonized water.
According to a further embodiment of the present invention, the new process comprises the steps of:
treating the semiconductor device with an aqueous ammonia or ammonium hydroxide solution containing ozone for a time sufficient to effectively remove said post-etch residues or polymers from the surface thereof, and then rinsing the semiconductor device with ozonized water.
The features and advantages of the process according to the invention will be better understood from the following description of preferred embodiments thereof, given by way of non-limitative example with reference to the accompanying drawings.